The Calcium Sulfate Dihydrate plant, with a production of 17,000 tons per year, will be established in Karang Rejo, Manyar District, East Java, on a 45,000 m² site. The raw materials, iron and sulfuric acid, will be supplied by PT Gunawan Dian Jaya Steel and by PT Petrokimia Gresik, respectively. The plant is designed to operate continuously for 330 days per year, employing a workforce of 145 people.

The production process begins with iron and sulfuric acid reacting in a stirring tank reactor (RTB) at 70, 1 atm pressure, and exothermic reaction conditions. The result of the reaction in the form of iron (II) sulfate in the form of slurry and the by-product in the form of H2 gas which will be converted into a liquid phase through a compressor and cooler then for the slurry to flow through a series of processing units, such as product mixers, crystallizers, centrifuges, rotary dryers, ball mills and screens) to separate and purify the final product

The utility unit provides a total water need of 237,776.7 m³/day obtained from the Bengawan Solo River, electricity of 361,475.3 kW obtained from 2 generator units, and fuel for generator needs of 66,071 liters/hour and boiler needs of 42,885 liters/hour to support factory operations. In addition, the steam requirement is 626,8350 kg/hour.

Based on economic evaluation, the Fixed Capital Investment (FCI) required is Rp 458.836.243.306, with Working Capital (WC) of Rp 115.534.648.692. The Return on Investment (ROI) is 28% before tax and 18% after tax. The Pay Out Time (POT) is 2,62 years before tax and 3,53 years after tax. The Break-Even Point (BEP) is achieved at 45%, while the Shut Down Point (SDP) is at 24%. The project's Discounted Cash Flow Rate (DCFR) is 13%.

From both technical and economic perspectives, the ferrous sulfate heptahydrate plant is feasible for further consideration in the next planning stage.